Labyrinth seal system

ABSTRACT

A labyrinth seal system of the present invention is found in a motor having a ball bearing ring, a shaft, and a labyrinth seal washer. The ball bearing ring has an inner bearing ring with an inner ring surface. In one embodiment the labyrinth seal system includes a shaft having a first shaft portion with a first shaft diameter and a second shaft portion with a second shaft diameter. The first shaft portion has a first outer shaft surface and the second shaft portion has a second outer shaft surface. A shaft shoulder may be formed between the first and second outer shaft surfaces. The second outer shaft surface is at least partially annularly adjacent the inner ring surface. Also included is a labyrinth seal washer having an annular leg that is positioned at least partially between the first outer shaft surface and the inner ring surface. The labyrinth seal system includes turbulence zones interspersed with narrow flow zones.

BACKGROUND OF THE INVENTION

The following invention relates to a labyrinth seal for use inelectronic spindle motors having ball bearing rings.

As shown in FIG. 1, electric spindle motors of the type used in diskdrives conventionally use ball bearing rings 18 to facilitate movementbetween a rotary member and a stationary member. Ball bearing rings 18generally include metallic or ceramic ball bearings 20 which arepositioned between an inner bearing ring 22 and an outer bearing ring24. Bearing rings 18 may be either inner or outer rotators depending onwhether the hub 26 or shaft 28 rotates. Inner rotators have an innerbearing ring 22 which rotates, and outer rotators have an outer bearingring 24 which rotates. The ball bearings 20 are preferably evenly spacedwithin the inner and outer bearing rings 22 and 24. The ball bearings 20are generally held in this evenly spaced position by teeth of a ballbearing cage (not shown).

Bearing lubricant fluid is used in bearing rings 18 to encourage freemovement of the ball bearings 20, inner bearing ring 22, and outerbearing ring 24. Conventionally, the lubricant is initially deposited onthe teeth of the bearing cage. During use, however, the lubricant tendsto migrate and eventually escapes the bearing ring 18. The lubricantthat migrates and escapes the bearing ring 18 often enters the interiorof the motor or exits the motor completely.

One cause of lubricant migration is the rotation of the bearing ring 18and gravitational pull that causes the lubricant to be thrown from thebearing ring 18. Although lubricant generally is not thrown from abearing ring 18 at lower rotation speeds, higher rotation speeds tend todisperse or "sling out" lubricant. At particularly high speeds thelubrication is atomized.

Another cause of lubricant migration is airflow through the motor andbearing rings 18 which tends to push lubricant, particularly atomizedlubricant, out of the bearing ring 18. Airflow also tends to carryparticles and contaminants. The use of bearing shields 30 reduces theflow of air and contaminants through the bearing ring 18 and therebypartially inhibits the loss of lubricant from the bearing ring 18.

Once the lubricant escapes the bearing ring 18 it enters the horizontalgap 32 between the top surface of the ball bearing ring 18 and thebottom surface of the washer 34 (or other enclosing apparatus). Thelubricant then travels from the gap 32 up through the vertical air gap36 between the inner surface 38 of the washer 34 and the smooth outersurface 39 of the shaft 28. The lubricant then can escape the motor.

Using fluid labyrinths to prevent lubrication fluid from escaping afluid bearing spindle motor is shown in U.S. Pat. No. 5,536,088 which isassigned to the same assignee as the present application, the disclosureof which is hereby incorporated by reference. Fluid labyrinths found insuch fluid bearing spindle motors are generally the winding path inwhich the lubrication fluid resides, at least part of which forms thefluid bearings.

Fluid labyrinths are not used with ball bearing spindle motors becausethe lubrication fluid is not intended as a bearing but instead is usedto facilitate rotation between the ball bearings 20 and the inner andouter bearing rings 20, 24. Accordingly, the lubrication fluid is notintended to enter the air gaps 32 and 36.

SUMMARY OF THE INVENTION

A labyrinth seal system of the present invention significantly preventslubricant escaping the motor.

A motor incorporating the labyrinth seal system includes at least onerotating member that rotates in relation to another member. The rotatingmember is separated from the other member by a ball bearing ring thathas an inner bearing ring and an outer bearing ring separated by aplurality of ball bearings. The inner bearing ring has an inner ringsurface.

The labyrinth seal system may also include a shaft having a first shaftportion with a first shaft diameter and a second shaft portion with asecond shaft diameter. The first shaft diameter is narrower than thesecond shaft diameter. The first shaft portion has a first outer shaftsurface and the second shaft portion has a second outer shaft surface. Ashaft shoulder may be formed between the first and second outer shaftsurfaces. The second outer shaft surface is at least partially annularlyadjacent the inner ring surface.

A labyrinth seal washer is also included in the present invention. Thelabyrinth seal washer has an annular leg positioned at least partiallybetween the first outer shaft surface and the inner ring surface.

As configured, the labyrinth seal system includes a first turbulencezone between the lower seal surface and the upper ring surface. A firstnarrow flow zone is formed between the inner ring surface and the outerleg surface. A second turbulence zone is then formed between the shaftshoulder and the leg tip. Finally, a second narrow flow zone is formedbetween the inner leg surface and the first outer shaft surface.

One advantage of the present invention is the longer path that thelubricant has to follow makes it more difficult for lubricant to escapethe motor. Since the lubricant has to flow farther to exit the motor,the longer path effectively creates a seal.

Another advantage of the present invention is that the radial openingleading to the exterior of the motor (between the shaft and the leg ofthe labyrinth seal washer) is generally smaller than the radius of theinner bearing ring opening. The reduced radius is significant because itmeans that the radial opening has less surface area for automizedlubricant to flow from the motor.

Yet another advantage is that gaps between the LSW, shaft, and bearingmay act as turbulence zones. By increasing turbulence the flow of thelubricant is slowed.

A final advantage is that the path created by the LSW, in which theescaping lubricant flows has several corners which cause the lubricantto change the direction in which it is flowing. Each change of directioncauses the lubricant to have an energy loss. The turns, like the gapsalso tend to create turbulence zones by "stirring up" the lubrication.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side sectional view of a known ball bearing ring andseal washer.

FIG. 2 is a partial side sectional view of a ball bearing ring andlabyrinth seal washer of the present invention.

FIG. 3 is an expanded side sectional view of the labyrinth seal of thepresent invention.

FIG. 4 is a modified embodiment of a ball bearing ring and labyrinthseal washer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIGS. 2 and 3, the present invention is a labyrinth sealsystem formed by substituting a labyrinth seal washer (LSW) 40 for thestandard, flat washer 34 (FIG. 1) of conventional motors. Shown in crosssection, the LSW 40 is L-shaped. Accordingly, the LSW 40 has an annularleg 42 that projects downward and, when in position, is in a spacedannularly relationship to the shaft 28.

As set forth above, like a standard motor, motors incorporating thepresent invention include a bearing ring 18. The inner bearing ring 22and the outer bearing ring 24 are separated by a plurality of ballbearings 20. The inner bearing ring 22 has an inner ring surface 44substantially adjacent the shaft 28 and the outer bearing ring 24 has anouter ring surface 46 adjacent the hub 26. Because the inner bearingring 22 and the outer bearing ring 24 can rotate freely relative to eachother, either the shaft 28 or the hub 26 can rotate depending on thedesign of the motor.

As shown, the leg 42 of the labyrinth seal washer 40 is positioned atleast partially between the outer surface 47 of the shaft 28 and theinner ring surface 44 of the inner bearing ring 22. Having the annularleg 42 positioned between the shaft 28 and inner bearing ring 22 has notbeen done before because it was necessary that the bearing ring 18 becentrifugally locked or physically fixed to the shaft 28. Using thedesign as set forth below, however, calculation has shown that the bondstrength between the inner bearing surface 44 and the shaft 28 issufficient if at least 60% of the inner ring surface 44 is adjacent theshaft 28. This fact permitted the leg 42 to be positioned at leastpartially between the inner bearing ring 22 and the shaft 28.

To accommodate the leg 42 between the inner bearing ring 22 and theshaft 28, a gap partially therebetween had to be created. Accordingly,in one embodiment an annular notch was created in the standard shaft 28to accommodate the annular leg 42 of the LSW 40. More specifically, inthis embodiment, the shaft 28 has a first shaft portion 28a with a firstshaft diameter 48a and a second shaft portion 28b with a second shaftdiameter 48b. The first shaft diameter 48a is narrower than the secondshaft diameter 48b. In this manner, the first shaft portion 28a isnarrower than the second shaft portion 28b. The short jog 49 between thefirst shaft portion 28a and the second shaft portion 28b appears as ashoulder.

The first shaft portion 28a has a first outer shaft surface 50a and thesecond shaft portion 28b has a second outer shaft surface 50b. Theannular leg 42 has an inner leg surface 52a and an outer leg surface52b. The first outer shaft surface 50a is at least partially annularlyparallel the inner leg surface 52a. Further, the second outer shaftsurface 50b is at least partially annularly adjacent the inner ringsurface 44 of the inner bearing ring 22. Still further, the inner ringsurface 44 is at least partially annularly parallel the outer legsurface 52b. In other words, the inner ring surface 44 is partiallyannularly parallel both the outer leg surface 52b and the second outershaft surface 50b.

When the LSW 40 is in place, there are turbulence zones 54a and 54b andnarrow flow zones 56a and 56b that are formed between the surfaces ofthe bearing ring 18, LSW 40, and shaft 28. More specifically, a firstturbulence zone 54a is formed between the lower surface 58 of the LSWand the upper surface 60 of bearing 18 (including the bearing shield 30if there is one). A first narrow flow zone 56a is formed between theinner ring surface 44 and the outer leg surface 52b. The secondturbulence zone 54b is formed between the tip 62 of leg 42 and the jog49 of the shaft 28. Finally, the second narrow flow zone 56b is formedbetween the inner leg surface 52a and the first outer shaft surface 50a.

After the atomized lubricant leaves the bearing ring 18 it is carried byairflow into the first turbulence zone 54a. From the first turbulencezone 54a, the airflow then carries the atomized lubricant into the firstnarrow flow zone 56a, the second turbulence zone 54b, and finally intothe second narrow flow zone 56b.

The alternation of narrow flow zones 56a, 56b and wide turbulence zones54a, 54b is significant. In the wide turbulence zones 54a, 54b thepressure of the flow is increased and the velocity is decreased. In thenarrow flow zones 56a, 56b the pressure of the flow is decreased and thevelocity is increased. By increasing the turbulence, the flow of theescaping lubricant is slowed.

FIG. 4 shows an alternate embodiment that includes a standard shaft 28,a modified ball bearing ring 64, and a LSW 40. The modified ball bearingring 64 is substantially identical to standard ball bearing rings exceptthat it has a modified inner bearing ring 66 that has an annular notch68 in an upper corner 70. The annular notch 68 accommodates the annularleg 42 of the LSW 40. In this embodiment, turbulence zones and narrowflow zones are also formed. More specifically, a modified firstturbulence zone 74a is formed between the lower surface 58 of LSW 40 andthe upper surface 60 of modified bearing 64. A modified first narrowflow zone 76a is formed between the notch surface 78 parallel to theshaft 28 and the outer leg surface 52b. The modified second turbulencezone 74b is formed between the tip 62 of leg 42 and the notch surface 80perpendicular to the shaft 28. Finally, the modified second narrow flowzone 76b is formed between the inner leg surface 52a and the outer shaftsurface 82.

It should be noted that shown bearing ring 18 is meant to be exemplary.In alternate embodiments the bearing ring may include no shields, oneshield, or two shields as shown. The shields may be integral, as shown,or may be external such as the shields shown in U.S. patent applicationSer. No. 08/581,058 which is assigned to the same assignee as thepresent application, the disclosure of which is hereby incorporated byreference.

Finally, it should be noted that the bearing lubricant may be anylubricant such as oil. Preferably, the lubricant includes a rustinhibiting agent. Further, the lubricant may be a combination of a baseand grease.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

What is claimed is:
 1. In a motor having at least one rotating member, alabyrinth seal system comprising:(a) a ball bearing ring including aninner bearing ring and an outer bearing ring separated by a plurality ofball bearings, said inner bearing ring having an inner ring surface; (b)a shaft having a first shaft portion with a first shaft diameter and asecond shaft portion with a second shaft diameter, said first shaftdiameter being narrower than said second shaft diameter, said firstshaft portion having a first outer shaft surface and said second shaftportion having a second outer shaft surface, said second outer shaftsurface at least partially annularly adjacent said inner ring surface;(c) a labyrinth seal washer having an annular leg positioned at leastpartially between said first outer shaft surface and said inner ringsurface, said leg having an inner leg surface and an outer leg surface;(d) a first narrow flow zone between said inner ring surface and saidouter leg surface; and (e) a second narrow flow zone between said innerleg surface and said first outer shaft surface.
 2. In a motor having abearing ring having an upper ring surface and an inner ring surface, ashaft having a first shaft portion with a first outer shaft surface anda second shaft portion with a second outer shaft surface, a shaftshoulder formed between said first and second outer shaft surface, and alabyrinth seal washer having an annular leg, said labyrinth seal washerhaving a lower seal surface, and said annular leg having an inner legsurface, an outer leg surface, and a leg tip, a labyrinth seal systemcomprising:(a) a first turbulence zone between said lower seal surfaceand said upper ring surface; (b) a first narrow flow zone between saidinner ring surface and said outer leg surface; (c) a second turbulencezone between said shaft shoulder and said leg tip; and (d) a secondnarrow flow zone between said inner leg surface and said first outershaft surface.
 3. A labyrinth seal system comprising:(a) a shaft havingan outer shaft surface, said shaft having a first shaft portion and asecond shaft portion; (b) a bearing ring surrounding said shaft, saidbearing ring having an inner ring surface at least partially adjacentsaid outer shaft surface; (c) a labyrinth seal washer having an annularwasher surface and an annular leg, said annular leg perpendicular saidannular washer surface; (d) said annular leg at least partially betweensaid outer shaft surface and said inner ring surface, said annular leghaving an inner leg surface and an outer leg surface; (e) a first narrowflow zone between said inner ring surface and said outer leg surface;and (f) a second narrow flow zone between said inner leg surface andsaid first the outer surface of said first shaft portion.
 4. The sealsystem of claim 3 wherein said first shaft portion is parallel saidinner leg surface, and said outer leg surface and said second shaftportion is parallel said inner ring surface.